Organohalosilanes, alkoxysilanes, halosilanes, and in particular methylchlorosilanes, are the building blocks from which silicone polymers are produced. Organohalosilanes and halosilanes are commercially produced by what is commonly called “the direct process”, in which silicon metal is reacted with an organic halide or hydrogen chloride, optionally in the presence of a catalyst. The direct process is well known in the art, and is described for example in U.S. Pat. No. 2,380,995. For example, in the commercial production of methylchlorosilanes by the direct process, finely ground silicon metal powder is reacted with methyl chloride in the presence of a catalyst by fluidising the silicon powder in a fluid bed by passing methyl chloride gas there through at a temperature of between 200° C. and 500° C.
As well as methylchloromonosilanes and/or chloromonosilanes, the direct process and other processes for the production of organic silicon compounds or silicon halides from silicon metal produce higher boiling point silicon compounds, particularly higher boiling point halosilanes, which are chemically active materials. Once separated from the other reaction products of the direct process, these higher boiling point silicon compounds can be hydrolysed to obtain a gel-solids mixture, referred to hereinafter as “Silicone gel”, which is a mixture of hydrolysed silicon compounds. Methods of producing such a solid or granular Silicone gel are described for example in U.S. Pat. No. 4,408,030, U.S. Pat. No. 4,690,810 and U.S. Pat. No. 5,876,609.
The present inventors have now found a useful way of processing Silicone gel or other hydrolysed silicon compounds into ceramic articles which demonstrate improved physical and/or physicochemical properties.